Virtually all motorcycles utilize some type of frame structure to carry loads encountered during vehicle operation. One type of frame structure known as a twin-spar frame typically uses a pair of large cross section aluminum beams that extend from the motorcycle steering head and around the sides of the engine to the swingarm pivot. As such, the engine is at least partially surrounded by frame structure on its right and left sides. Another type of frame structure is known as a cradle frame. The cradle frame generally includes one or more structural members extending over the top of the engine, and one or more structural members extending below the engine. Both types of frames support a wide variety of motorcycle components including the engine, fuel tank, seat, and footpegs, as well as other items.
Most motorcycle frames, whether twin-spar or cradle style, are fabricated (e.g. cast and/or welded) as one-piece assemblies. Several limitations arise when a motorcycle frame is fabricated as a single piece. While the unitary construction is generally very strong, installation and removal of the engine are often difficult, especially when it is aesthetically desirable to package the engine as tightly within the frame as possible. Furthermore, alterations to the frame, such as relocation of the footpegs or other items that mount to the frame, can be difficult and time consuming. For a consumer, such alterations generally require cutting, grinding, and welding of the frame, all of which may weaken the frame as well as detract from its appearance. For a manufacturer that may want to develop an entire vehicle line using a single style of frame, such minor alterations often require expensive new tooling and/or fabrication equipment.
Therefore, a new motorcycle frame that facilitates installation and removal of the engine and simplifies the process of relocating certain motorcycle components, while simultaneously fulfilling the structural requirements of a motorcycle frame would be welcomed by those in the art.